260 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY-GENERAL REPORT. 
hairy around the naked tubercles, and the hairs on the ears longer than in the. preceding 
(summer?) specimens. Killed December 3, 1852. Head, 3 inches; head and body, 11; tail 
vertebrae, 9 ; tail vertebrae, with hairs, 11. (No. 1*78, Detroit, Michigan.) 
6 th. Similar to the last', but tail distinctly annulated with brown. Soles more hairy. The 
hairs of the convexity of the ear still longer. (Winter, No. *720, Cook county, Illinois.) 
7th. Colors above lighter, like a rather dusky gray squirrel. Hairs on the under surface of 
body with more brownish rusty ; less black. Tail hairs annulated distinctly ; their tips whitish 
or rusty gray. Soles more naked. Hair on the ears shorter. (Spring, No. 721, Cook county, 
Illinois.) 
8 th. General character that of a gray squirrel. Nose, inside of thighs, and region around 
genitalia dusky. Hairs annulated. Under surface, from chin to thighs, brownish rusty. 
The hairs annulated or tipped with blackish ; a narrow streak on each side the median line of 
the belly grayish while. Tail as in gray squirrels. Soles naked. (July, 1853, $ , No. 256, 
Eacine ; 257 similar.) 
9th. Similar to the last, but with no dusky on the inside of the thighs. Hairs of under 
surfaces only annulated on the throat and neck, where they are tinged with gamboge yellow. 
(No. 970, West Northfield, Illinois.) Another specimen with the light stripes on the belly 
larger, purer white, and confluent in places. The region around the teats is, however, more 
dusky than elsewhere. (No. 1136, Fort des Moines, Iowa.) 
10th. Chin and inside of the fore legs suffused with brownish ; an indistinct stripe of pale 
brown on each side of the median line of the belly. No annulation of inferior hairs. (No. 
1672, Carlisle, Pa.) 
11th. The next stage is the regular gray squirrel, in which the prevailing color of the hairs 
above is gray, with subterminal annulations of black, more or less concealed by the gray tips. 
The entire under parts are white ; the sides of the white with a narrow margin on the flanks of 
yellowish rusty. This color also overlays the gray of the upper parts in varying proportions, 
sometimes confined to the head ; sometimes along the middle of the back as a narrow stripe; 
sometimes as a broader one ; sometimes forming a cross across the shoulders ; sometimes forming 
a uniform wash over the whole surface. The proportion of yellow also varies considerably. 
The ears are generally of a yellowish brown color, rather lighter at the posterior surface. 
In summer, the hair is everywhere very short, and uniform in length. With the approach of 
cold weather, it lengthens on the convex postero-internal surface of the ear, except along a 
narrow anterior margin. A similar lengthening takes place in a small patch on the neck at 
the base of the ear behind. These lengthened hairs, being white and woolly in appearance, 
form a conspicuous mark, not nearly so appreciable, if at all, in summer. The extreme border 
of the ear, however, (about one-tenth to one-twentieth of an inch wide,) remains short-haired, 
and of a rusty yellow color, strongly contrasted against the woolly white. 
Coincident with this change of hair on the ears is a similar one on the soles. In summer 
these are entirely free from hair, except for about half an inch from the extreme heel, which is 
densely furred. The naked space commences in a transverse line about as far behind the pos¬ 
terior tubercle as its own length. With the approach of cold weather, hairs begin to grow on 
the soles until, in midwinter, they are completely covered with close, short hairs, except on the 
five large tubercles and the balls of the toes, and perhaps a short distance behind them. In 
many cases, too, a similar development of hairs takes place between the tubercles of the palms. 
Although in more northern specimens the amount of growth of fur on the ears and soles is 
